Re: bignums

[gisle@apal.ii.uib.no (Gisle Sælensminde)]

In article <9jk3th$knr$1@news.huji.ac.il>, Ehud Lamm wrote:
>Tomasz Wegrzanowski <taw@pb220.legnica.sdi.tpnet.pl> wrote in message
>news:9jifep$kf0$2@news.tpi.pl...
>> Is there any unlimited-size-integer thing in Ada,
>> something like gmp in C ?
>
>There are two issues here. First, support for bignums: there are some
>package around, and it isn't too hard to hack something.
>The second issue is efficiency. I seem to recall that GMP is highly
>optimized, uses assembly language etc. So one  may actually want or hope for
>a binding to GMP. I don't know a thing about it, but I did find this web
>page http://www.chiark.greenend.org.uk/~mroe/Ada/GMP/. Maybe someone knows
>more about the current status of this.

I also wrote a binding for GMP, and have finished the integer part of it,
including a thick binding, but not for rationals and floats. I had plans 
to develop the rest when I have made the thick binding for floats as 
well, but the project stop since I personally only needed integers, and 
the float stuff seems to be crap, so I stoped there without finishing the 
project. I if anybody are interested I can put the bits together and 
relese it.

There is one problem by making a thick binding for a library like GMP.
Of cause the most natural way of making a thick binding is to use
operator overloading, so that you can make code like "A = B + C;".

The problem is that each new GMP number is dynamically allocated,
and for uing it with operator overloading you must make a controlled 
type and allocate a new new number for each operation. This leads to
very slow code, compared to the thin binding. In my fibonacci test
there were a 1:6 difference between them.

A better Idea then would be to write a new binding where one could use
Ada's capability to allocate the numbers on the stack. I was member of a 
mailing list where we started looking at this, but it ended because 
all of us were having (final) exams at the time.

- Gisle

>
>
>HTH
>
>Ehud Lamm
>
>


-- 
--
Gisle S�lensminde ( gisle@ii.uib.no )   

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